Hi Markus,
Thank you for posting here.
Could you please tell us what version of C# and Visual Studio you are using? Because according to the error message of your second link, it seems that this error is caused by the C# version is too old.
Best Regards,
Timon
MSDN Community Support
Please remember to click "Mark as Answer" the responses that resolved your issue, and to click "Unmark as Answer" if not. This can be beneficial to other community members reading this thread. If you have any compliments or complaints to
MSDN Support, feel free to contact MSDNFSF@microsoft.com.
